JP5692849B2 - Manufacturing method of glass substrate for mask blank, manufacturing method of mask blank, and manufacturing method of transfer mask - Google Patents

Description

  The present invention relates to a mask blank substrate used for manufacturing a photomask (transfer mask) used in manufacturing an electronic device such as a semiconductor device, a mask blank and a transfer mask manufacturing method, and a transfer mask cleaning method. About.

 In general, in a manufacturing process of a semiconductor device, a fine pattern is formed using a photolithography method. Also, a number of substrates called photomasks (hereinafter referred to as “transfer masks”) are usually used to form this fine pattern. This transfer mask is generally provided with a fine pattern made of a metal thin film on a translucent glass substrate, and the photolithographic method is also used in the production of this transfer mask.

 In manufacturing a transfer mask by photolithography, a mask blank having a thin film (for example, a light shielding film) for forming a transfer pattern (mask pattern) on a light-transmitting substrate such as a glass substrate is used. In the manufacture of a transfer mask using this mask blank, an exposure process for drawing a desired pattern on the resist film formed on the mask blank, and developing the resist film in accordance with the desired pattern drawing, the resist pattern is developed. The development step is formed, the etching step is to etch the thin film in accordance with the resist pattern, and the step is to remove and remove the remaining resist pattern. In the developing step, a desired pattern is drawn on the resist film formed on the mask blank, and then a developing solution is supplied to dissolve a portion of the resist film that is soluble in the developing solution, thereby forming a resist pattern. . In the etching step, the resist pattern is used as a mask to dissolve the exposed portion of the thin film on which the resist pattern is not formed by dry etching or wet etching, thereby forming a desired mask pattern on the light-transmitting substrate. Form. Thus, a transfer mask is completed.

  By the way, in the manufacturing process of the glass substrate for mask blank used for manufacture of the said transfer mask, the washing | cleaning for removing the particle | grains (foreign material etc.) which exist on a substrate surface with respect to the glass substrate after mirror polishing is carried out. Has been done. Conventionally, several methods are known for this cleaning. As one of the methods, a method of cleaning the substrate surface by directly applying cleaning water to which an ultrasonic wave of about 1 MHz is applied to the substrate surface (hereinafter referred to as “cleaning”). "Megasonic cleaning"). In the case of conventional cleaning with sulfuric acid / aqueous ammonia, the smoothness and flatness of the glass substrate surface obtained by polishing may be deteriorated. Since the megasonic cleaning does not have such a defect, it is suitable for a mask blank substrate in which the demand for higher quality is becoming more severe. In Patent Document 1, a cleaning liquid obtained by mixing ozone water or anode water with hydrogen water or cathode water, and applying ultrasonic waves to the cleaning liquid to clean a precision substrate such as a mask blank substrate, is used. A method is disclosed. Further, Patent Document 2 discloses one of physical cleaning methods for removing foreign substances adhering to a substrate surface using a physical action after etching the surface of a light-transmitting substrate using an etching solution. For example, it is disclosed that megasonic cleaning is performed by supplying a cleaning liquid in which ultrasonic waves are applied to the surface of a translucent substrate.

JP 2001-96241 A Japanese Patent Application Laid-Open No. 2005-221928

However, the present inventor has found that the conventional megasonic cleaning has the following problems.
In this megasonic cleaning method, when cleaning is performed by directly applying cleaning water to which the ultrasonic wave having a relatively low frequency in the MHz band, for example, a frequency of 1.5 MHz or less, is applied to the surface of the glass substrate, The action of peeling off the deposits is high, and a very high cleaning effect is obtained. However, the vibration given to the molecular structure constituting the surface layer of the glass substrate is also large, and there are cases in which latent scratches occur in a portion where the internal bonding structure is weaker than the surroundings. However, it has been very difficult to detect this latent flaw by conventional defect inspection of the substrate. For this reason, the substrate having latent scratches in the surface layer may be sent to the next thin film forming step as an acceptable product, and a transfer pattern forming thin film may be formed and shipped as a mask blank for the acceptable product.

  When a mask for transfer is made using a mask blank in which latent scratches are inherent in the surface layer of such a substrate, the etchant acts on the latent scratches during the etching process when forming a transfer pattern on the pattern forming thin film. There was a risk of manifesting as a concave defect. In addition, a cleaning process at the time of producing a transfer mask, a cleaning process of a transfer mask that is periodically performed when continuously used as a transfer mask, particularly cleaning using a cleaning liquid having an etching action on a glass substrate ( In a cleaning process in which alkali cleaning or the like is performed, there is a possibility that the cleaning liquid may appear as a concave defect by acting on a latent flaw inherent in the surface layer of the substrate. In particular, when latent scratches are present in the surface layer of the main surface of the substrate on the side where the transfer pattern forming thin film is formed, the etchant or the cleaning liquid contacts the surface layer of the main surface of the substrate in these etching processes and cleaning processes. Since the substrate surface without a pattern is an exposed light-transmitting portion, if a concave defect is formed there, a transmittance abnormality or phase abnormality occurs, and the substrate cannot be used as a transfer mask. In addition, when the latent scratch becomes apparent as a concave defect, the transfer pattern that is in contact with the concave defect may fall off, and such a transfer mask cannot be used continuously.

  On the other hand, in the case where megasonic cleaning is performed after the transfer pattern forming thin film is formed on the main surface of the mask blank glass substrate, the same problem that latent scratches occur on the surface layer of the substrate occurs. In particular, when latent scratches occur on the surface of the main surface of the substrate on the side where the transfer pattern forming thin film is formed, the surface layer of the main surface of the substrate cannot be exposed because it cannot be exposed by contact with an alkaline chemical solution or the like. There is no method for detecting a flaw, and there is a problem that the product is shipped as an acceptable mask blank.

Accordingly, the present invention has been made to solve such a conventional problem, and the object of the present invention is to use cleaning water to which ultrasonic waves are applied when cleaning a mask blank substrate. To provide a method for manufacturing a mask blank substrate having a cleaning step that can suppress the occurrence of latent scratches inside a glass substrate even when a cleaning method is applied, and can reliably eliminate particles present on the main surface of the substrate. It is.
Second, even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied when cleaning the mask blank, it is possible to suppress the occurrence of latent scratches inside the glass substrate, and the transfer pattern forming thin film It is providing the manufacturing method of the mask blank which has the washing | cleaning process which can exclude the particle which exists on the surface of this.

  Third, even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied when cleaning the transfer mask, it is possible to suppress the occurrence of latent scratches inside the glass substrate and to be present on the mask surface. It is an object of the present invention to provide a transfer mask cleaning method that can surely eliminate particles to be transferred.

As a result of earnest research to solve the above problems, the present inventor can suppress the occurrence of latent scratches inside the glass substrate by optimizing the frequency of the ultrasonic wave applied to the cleaning water, and also the main surface of the substrate In addition, it has been found that particles existing on the surface of the transfer pattern forming thin film of the mask blank, particularly particles having a particle size of 60 nm or more, for example, can be surely excluded.
The present inventor has completed the present invention as a result of further intensive studies based on the above elucidated facts.
That is, in order to solve the above problems, the present invention has the following configuration.

(Configuration 1)
A mask blank substrate comprising a cleaning step of cleaning a surface of a substrate by applying cleaning water to which an ultrasonic wave having a frequency higher than 1.5 MHz is applied toward the surface of the substrate made of a glass material. It is a manufacturing method.
(Configuration 2)
The mask blank substrate manufacturing method according to Configuration 1, wherein an ultrasonic frequency applied to the cleaning water is 5.0 MHz or less.

(Configuration 3)
3. The method for manufacturing a mask blank substrate according to Configuration 1 or 2, wherein a removal rate of particles having a particle size of 60 nm or more before cleaning on the surface of the substrate after cleaning is 95% or more. .
(Configuration 4)
4. The mask blank substrate according to any one of configurations 1 to 3, wherein the substrate is a binary mask blank substrate, a phase shift mask blank substrate, or a multi-tone mask blank substrate. Is the method.

(Configuration 5)
A mask blank, characterized in that a thin film for forming a transfer pattern is formed on the surface of a mask blank substrate obtained by the method for manufacturing a mask blank substrate according to any one of configurations 1 to 4. It is a manufacturing method.
(Configuration 6)
A film forming process for forming a thin film for forming a transfer pattern on the surface of a substrate made of a glass material, and cleaning water to which an ultrasonic wave having a frequency higher than 1.5 MHz is applied toward the surface of the thin film. And a cleaning process for cleaning the surface of the thin film.

(Configuration 7)
The mask blank manufacturing method according to Configuration 6, wherein the frequency of ultrasonic waves applied to the cleaning water is 5.0 MHz or less.
(Configuration 8)
8. The method of manufacturing a mask blank according to Configuration 6 or 7, wherein a removal rate of particles having a particle size of 60 nm or more before cleaning on the surface of the thin film after cleaning is 95% or more.

(Configuration 9)
The mask blank manufacturing method according to any one of Structures 6 to 8, wherein the mask blank is a binary mask blank, a phase shift mask blank, or a multi-tone mask blank.
(Configuration 10)
A transfer mask manufacturing method, wherein a transfer pattern is formed by patterning the thin film of a mask blank obtained by the mask blank manufacturing method according to any one of Structures 5 to 9.

(Configuration 11)
A transfer mask characterized by cleaning the surface of the transfer mask by applying cleaning water to which an ultrasonic wave having a frequency higher than 1.5 MHz is applied toward the surface of the transfer mask on which the transfer pattern is formed. This is a cleaning method.
(Configuration 12)
12. The method for cleaning a transfer mask according to Configuration 11, wherein the frequency of ultrasonic waves applied to the cleaning water is 5.0 MHz or less.

  According to the mask blank substrate manufacturing method of the present invention, when a cleaning method using cleaning water to which ultrasonic waves are applied is applied during cleaning of the mask blank substrate, the ultrasonic frequency is higher than 1.5 MHz. By applying the cleaning water to which the is applied to the surface of the substrate for cleaning, it is possible to suppress the occurrence of latent scratches inside the glass substrate, and to reliably eliminate particles present on the main surface of the substrate. Moreover, by producing a mask blank and a transfer mask using the mask blank substrate obtained by the present invention, it is possible to suppress the occurrence of concave defects due to latent scratches inside the substrate, and the transmittance of the transfer mask. Abnormality and phase abnormality can be prevented from occurring.

  Moreover, according to the mask blank manufacturing method of the present invention, even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied when cleaning the mask blank, ultrasonic waves having a frequency higher than 1.5 MHz are applied. By applying the washed cleaning water to the surface of the mask blank thin film, it is possible to suppress the occurrence of latent scratches inside the glass substrate even when the mask blank is cleaned, and to be present on the surface of the transfer pattern forming thin film. Particles can be surely eliminated. By producing a transfer mask using the mask blank obtained according to the present invention, it is possible to suppress the occurrence of concave defects due to latent scratches, and to prevent the occurrence of transmittance abnormality and phase abnormality of the transfer mask. . In addition, when cleaning the mask blank, that is, after the transfer pattern forming thin film is formed on the main surface of the mask blank substrate, the surface layer on the main surface of the substrate on the side where the transfer pattern forming thin film is formed. If there is a latent scratch on the surface, it cannot be made visible by contacting it with an alkaline solution, so there is no way to detect the mask blank where the latent scratch has occurred. Since the importance of not making it higher is higher, the effect of the present invention is very large.

  Further, according to the transfer mask cleaning method of the present invention, an ultrasonic wave having a frequency higher than 1.5 MHz is applied even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied at the time of cleaning the transfer mask. By applying the cleaning water applied to the surface of the transfer mask and cleaning it, it is possible to suppress the occurrence of latent scratches on the light-transmitting portion having no transfer pattern, and to reliably eliminate particles existing on the mask surface. . Therefore, even if the transfer mask is cleaned repeatedly (especially alkali cleaning), it is possible to suppress the occurrence of concave defects due to latent scratches, and to prevent the transfer mask from having an abnormal transmittance or phase. The transfer mask can be used continuously.

It is a block diagram which shows an example of the washing | cleaning apparatus used in the washing | cleaning process in this invention.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention cleans the surface of the substrate by applying cleaning water to which an ultrasonic wave having a frequency higher than 1.5 MHz is applied toward the surface of the substrate made of a glass material as in the invention of Configuration 1 above. It is a manufacturing method of the mask blank substrate characterized by having a washing process.

  The mask blank substrate made of the glass material is not particularly limited as long as it has transparency with respect to the exposure wavelength to be used. In the present invention, a quartz substrate and other various glass substrates (for example, soda lime glass, aluminosilicate glass, etc.) can be used. Among them, the quartz substrate is transparent in an ArF excimer laser or a shorter wavelength region. Therefore, it is suitable as a binary mask blank substrate or a phase shift mask blank substrate used for high-definition transfer pattern formation.

In the manufacturing process of the mask blank glass substrate, after the polishing process, a cleaning process is performed to remove particles present on the glass substrate surface (for example, foreign substances such as abrasive grains adhering to the substrate surface). Is done.
In the polishing step, the polishing pad is brought into contact with the surface of the mask blank substrate (glass substrate), a polishing liquid containing abrasive grains is supplied to the surface of the glass substrate, and the glass substrate and the polishing pad are moved relative to each other. To polish the surface of the glass substrate. For example, a glass substrate is pressed against a polishing surface plate to which a polishing pad is adhered, and the polishing surface plate and the glass substrate are relatively moved while supplying a polishing liquid containing polishing grains (that is, the polishing pad and the substrate are moved). By relatively moving), the surface of the glass substrate is polished. As the abrasive grains, colloidal silica is preferably used at least in the final polishing in the precision polishing step, because good smoothness and flatness of the glass substrate can be obtained. For this polishing step, for example, a planetary gear type double-side polishing apparatus or the like can be used.

In the present invention, after the polishing step, a cleaning step of cleaning the surface of the substrate by applying cleaning water to which an ultrasonic wave having a frequency higher than 1.5 MHz is applied toward the surface of the substrate made of a glass material. carry out.
According to the study of the present inventor, as described above, cleaning was performed by directly applying the cleaning water to which the ultrasonic wave having a relatively low frequency band of about 1 MHz, for example, a frequency of about 0.8 MHz, was applied to the surface of the glass substrate. In this case, although the action of peeling off the deposits on the substrate surface is high and a very high cleaning effect can be obtained, the vibration given to the molecular structure constituting the surface layer of the glass substrate is also large, and the internal bonding structure is relatively In some cases, latent damage occurred in weak areas. However, it is very difficult to detect such latent scratches in conventional substrate defect inspection, and etchants, alkaline cleaning liquids, etc. act on the latent scratches in the subsequent transfer mask manufacturing process and cleaning process. This is a serious problem that can be detected for the first time after being manifested as a defect, and if this concave defect is formed in the translucent part in a binary mask, phase shift mask, or multi-tone mask, a transmittance abnormality or phase abnormality occurs. It will be. Therefore, in the cleaning process after polishing the mask blank substrate, even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied, latent scratches are generated inside the glass substrate (particularly the surface layer of the substrate main surface). It is necessary to suppress.

  As a result of intensive studies to solve such problems, the present inventor has found that by optimizing the frequency of the ultrasonic wave applied to the cleaning water, it is possible to suppress the occurrence of latent scratches inside the glass substrate. . Specifically, by performing a cleaning step of cleaning the surface of the substrate by applying cleaning water to which ultrasonic waves having a frequency higher than 1.5 MHz are applied toward the surface of the glass substrate after polishing, It is possible to suppress the occurrence of latent scratches inside the substrate (particularly the surface layer of the substrate main surface). Moreover, it is preferable to apply cleaning water to which ultrasonic waves of 2.0 MHz or higher are applied because it is possible to more surely suppress the occurrence of latent scratches, and it is optimal to apply cleaning water to which ultrasonic waves of 2.5 MHz or higher is applied. . Whether or not latent scratches have occurred inside the substrate can be confirmed, for example, by making the latent scratches obvious with an alkaline chemical solution or the like.

  In addition, by applying a cleaning method that applies cleaning water to which ultrasonic waves are applied to clean the surface of the substrate, even if the cleaning water is applied with ultrasonic waves having a frequency higher than 1.5 MHz, the substrate Particles existing on the main surface can be surely eliminated. In the present invention, the upper limit of the frequency of the ultrasonic wave applied to the cleaning water is desirably 5.0 MHz or less. If the frequency of the ultrasonic wave applied to the cleaning water is higher than 5.0 MHz, the particle removal rate on the substrate surface after cleaning, particularly the removal rate of relatively large particles having a particle size of 200 nm or more may be lowered. Note that it is preferable to set the upper limit of the frequency of the ultrasonic wave applied to the cleaning water to 4.0 MHz or less because the removal rate of relatively large particles can be further improved. The upper limit of the frequency of the ultrasonic wave applied to the cleaning water is preferably 3 It is optimal when the frequency is 5 MHz or less.

  With the recent trend toward higher density and higher precision of electronic devices, transfer masks have become more finely patterned, and the requirements for surface smoothness and surface defects of mask blank substrates are becoming stricter year by year. Inspection accuracy has also improved, and surface defects with a small size (for example, a particle size equivalent to 60 nm) that cannot be confirmed by conventional inspection apparatuses are detected, and such minute surface defects are not allowed. It is coming.

According to the present invention, it is possible to obtain a high removal rate of 95% or more with respect to the surface of the substrate after cleaning with respect to particles having a particle size of 60 nm or more before cleaning. Here, the particle removal rate is a value calculated by the following relational expression.
Removal rate (%) = [(number of particles before cleaning−number of particles after cleaning) / number of particles before cleaning] × 100

  Specifically, particles containing a plurality of particle sizes (known) are applied on a substrate using a fine particle coating apparatus. For example, polystyrene latex (PSL) particles having a plurality of particle diameters of 60 nm or more (PSL particles have a characteristic that the probability that the particles are close to each other within 1 mm is 1% or less). It applies | coats with a predetermined | prescribed application density on a board | substrate. Then, the number of particles before cleaning is detected using a defect inspection apparatus such as a 60 nm sensitivity. The defect inspection apparatus having a sensitivity of 60 nm here refers to a defect inspection apparatus that can detect PSL particles even when a defect inspection is performed on a test body in which PSL particles having a particle diameter of 60 nm are dispersed on a substrate. After cleaning the substrate, the number of particles is similarly detected using the defect inspection apparatus. From these results, the removal rate of particles by cleaning is calculated by the above relational expression.

  In addition, when obtaining the removal rate of particles for each particle size rather than the removal rate of the entire particle including a plurality of particle sizes as described above, a plurality of particles are formed on the same substrate using a particle size fine particle coating apparatus. Apply only particles of known diameter. For example, PSL particles having a particle size of 60 nm, 90 nm, 120 nm, 150 nm, and 200 nm are coated on the same substrate with a predetermined coating density by dividing each region. Then, the number of particles for each particle diameter before cleaning is detected using a defect inspection apparatus such as a 60 nm sensitivity. After the substrate cleaning, the number of particles for each particle diameter is similarly detected using the defect inspection apparatus. From these results, the particle removal rate for each particle diameter by the cleaning is calculated by the above relational expression. According to the present invention, a particle removal rate of 95% or more can be obtained for any particle diameter of particles having a particle diameter of 60 nm or more.

FIG. 1 is a configuration diagram showing an example of a cleaning apparatus used in the cleaning process of the present invention.
A cleaning apparatus 10 shown in FIG. 1 is a single wafer cleaning apparatus, and includes a spin chuck 11 that holds a substrate 1 and an ultrasonic cleaning nozzle 14 provided at the tip of an arm 15. The spin chuck 11 is rotatably provided by an electric motor 12. Further, the ultrasonic cleaning nozzle 14 applies ultrasonic waves to the cleaning water supplied from the cleaning water supply device 16, and supplies the ultrasonic waves applied to the surface of the substrate 1 directly from above. At the time of cleaning, the ultrasonic cleaning nozzle 14 is configured to move (swing) from the center to the end surface of the substrate 1 by the arm 15 while rotating the substrate 1 at a predetermined number of rotations. The periphery of the spin chuck 11 is covered with a cleaning cup 13 to prevent the cleaning water from splashing.

In this case, it is preferable to use pure water as the cleaning water. If an acid or alkaline cleaning liquid such as conventional sulfuric acid perwater or ammonia perwater is used, the smoothness and flatness of the glass substrate surface obtained by polishing may be deteriorated. Note that hydrogen gas-dissolved water, O ₂ gas-dissolved water, O ₃ gas-dissolved water, rare gas-dissolved water, N ₂ gas-dissolved water, or the like may be applied to the cleaning water.

In the case of using the above-described cleaning apparatus, it is desirable that the number of rotations of the substrate during cleaning and the moving speed of the ultrasonic cleaning nozzle are appropriately set so that the entire substrate is cleaned uniformly. The flow rate of the cleaning water applied to the substrate surface is slightly different depending on the number of rotations of the substrate at the time of cleaning and the moving speed of the ultrasonic cleaning nozzle, but is preferably about 1.0 to 5.0 liters / minute. It is preferable to set it to about 0.0 to 3.0 liters / minute.
In addition, regarding the shape of the tip of the ultrasonic cleaning nozzle 14 in the above-described cleaning apparatus, for example, a circular shape or a rectangular shape (such as a slit shape) can be arbitrarily used.

As described above, according to the mask blank substrate manufacturing method of the present invention, when the mask blank substrate is cleaned, the frequency is 1.5 MHz even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied. By washing the surface of the substrate with cleaning water to which higher ultrasonic waves are applied, there is no possibility of latent scratches inside the glass substrate, and particles on the main surface of the substrate are surely eliminated. Can do.
In addition, by producing a mask blank and a transfer mask using the mask blank substrate obtained by the present invention, there is no possibility of generating a concave defect due to a latent scratch inside the substrate at the mask preparation stage or the mask cleaning stage. Thus, it is possible to prevent the transmission mask and the phase abnormality from occurring.

  The above is a description of the method for manufacturing a mask blank substrate according to the present invention. However, in the cleaning performed in the mask blank manufacturing stage, when applying a cleaning method using cleaning water to which ultrasonic waves are applied, the ultrasonic wave is a thin film. It has been found that latent scratches are generated by being transmitted from the surface to the inside of the substrate, and it is necessary to suppress this. If latent scratches are generated inside the substrate in the cleaning process at the time of manufacturing the mask blank, when a transfer mask is manufactured using the mask blank, there is a possibility that a concave defect due to the latent scratches inside the substrate may occur.

  The present invention also provides a method for manufacturing a mask blank, and suppresses occurrence of latent scratches in the substrate in a cleaning process during the manufacture of the mask blank. That is, the present invention has a film forming process for forming a thin film for forming a transfer pattern on the surface of a substrate made of a glass material, and a frequency is increased toward the surface of the thin film, as in the invention of configuration 6 above. And a cleaning step of cleaning the surface of the thin film by applying cleaning water to which ultrasonic waves higher than 1.5 MHz are applied.

  In the film forming step, a thin film for forming a transfer pattern is formed on the surface of the mask blank glass substrate. The mask blank to which the present invention is suitably applied is a binary mask blank or a phase shift mask blank for producing a transfer mask in which a transfer pattern is formed on a translucent substrate (glass substrate). Therefore, the thin film for forming the transfer pattern is a thin film made of a material containing a metal such as a transition metal, and includes a single layer and a stacked layer. As will be described in detail later, for example, a light shielding film made of a material containing a transition metal alone or a compound thereof such as chromium, tantalum, or tungsten, an etching mask film provided on the light shielding film, or the like can be given. Further, a light semi-transmissive film and a light shielding film made of a material containing a compound of transition metal silicide (especially molybdenum silicide) are also included.

  As a method for forming the thin film on the glass substrate, for example, a sputtering film forming method is preferably exemplified, but the present invention is not limited to the sputtering film forming method.

  In the present invention, after the film forming step, a cleaning step is performed for cleaning the surface of the thin film by applying cleaning water to which an ultrasonic wave having a frequency higher than 1.5 MHz is applied toward the surface of the thin film. .

  Even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied at the time of cleaning the mask blank, the cleaning water to which ultrasonic waves having a frequency higher than 1.5 MHz are applied is used for the mask blank surface, that is, for transfer pattern formation. By cleaning against the surface of the thin film, it is possible to suppress the occurrence of latent scratches inside the glass substrate even when the mask blank is cleaned, and to reliably eliminate particles present on the surface of the transfer pattern forming thin film. Can do. Therefore, by producing a transfer mask using the mask blank obtained by the present invention, it is possible to suppress the occurrence of a concave defect due to a latent scratch, and to cause an abnormality in the transmittance and phase of the transfer mask. Can be prevented. For example, if latent scratches occur in the mask blank substrate cleaning process described above, the latent scratches can be confirmed with an alkaline chemical solution or the like. It is possible to do this, however, when cleaning the mask blank, that is, after the transfer pattern forming thin film is formed on the main surface of the mask blank substrate, particularly on the side where the transfer pattern forming thin film is formed. When there is a latent scratch on the surface of the main surface of the substrate, there is no method for detecting the mask blank in which the latent scratch has occurred because there is no method for detecting the mask blank where the latent scratch has occurred. The importance of not causing latent scratches during cleaning is higher, and the effect of the mask blank manufacturing method of the present invention is very large. Note that it is preferable to set the frequency of the ultrasonic wave applied to the cleaning water to 2.0 MHz or higher because it is possible to surely suppress the occurrence of latent scratches, and it is optimal to set the frequency of the ultrasonic wave applied to the cleaning water to 2.5 MHz or higher.

  Also, when cleaning such a mask blank, a high cleaning effect is obtained by applying a cleaning method in which cleaning water to which ultrasonic waves are applied is directly applied to the surface of the thin film, and is present on the surface of the thin film. This is effective for reliably eliminating particles, particularly fine particles equivalent to 60 nm or more. In the present invention, the upper limit of the frequency of the ultrasonic wave applied to the cleaning water is desirably 5.0 MHz or less. If the frequency of the ultrasonic wave applied to the cleaning water is higher than 5.0 MHz, the particle removal rate on the surface of the thin film after cleaning, particularly the removal rate of relatively large particles having a particle size of 200 nm or more may be lowered. Note that it is preferable to set the upper limit of the frequency of the ultrasonic wave applied to the cleaning water to 4.0 MHz or less because the removal rate of relatively large particles can be further improved. The upper limit of the frequency of the ultrasonic wave applied to the cleaning water is preferably 3 It is optimal when the frequency is 5 MHz or less.

  According to the present invention, a removal rate of 95% or more of particles having a particle diameter of 60 nm or more on the surface of the thin film after cleaning is obtained. Here, the particle removal rate is synonymous with the particle removal rate after the cleaning of the mask blank substrate described above.

In the mask blank cleaning process, a cleaning apparatus as shown in FIG. 1 can be preferably used. It is preferable to use pure water as the cleaning water. In addition, hydrogen gas-dissolved water, O ₂ gas-dissolved water, O ₃ gas-dissolved water, rare gas-dissolved water, N ₂ gas-dissolved water, or the like may be applied to the cleaning water.
When using the above-described cleaning apparatus in the mask blank cleaning process, the rotation speed of the mask blank and the moving speed of the ultrasonic cleaning nozzle at the time of cleaning may be appropriately set so that the entire mask blank is cleaned uniformly. desirable. Further, the flow rate of the cleaning water applied to the mask blank surface is slightly different depending on the number of rotations of the mask blank at the time of cleaning and the moving speed of the ultrasonic cleaning nozzle, but is preferably about 1.0 to 5.0 liters / minute, In particular, the rate is preferably about 1.0 to 3.0 liters / minute.

  The mask blank substrate manufacturing method of the present invention and the mask blank manufacturing method of the present invention described above are particularly adapted to use exposure light (such as ArF excimer laser) having a short wavelength of 200 nm or less where a fine transfer pattern is required. It is suitable for manufacturing a mask blank substrate and a mask blank used for producing a transfer mask used in the exposure apparatus. The demand for pattern miniaturization is increasing more and more, and the demand for surface defects in mask blank substrates and mask blanks has become very severe. For example, when a phase shift mask is produced using a mask blank in which the above-described latent scratch occurs on the surface of the glass substrate or a convex defect due to adhesion of a foreign substance exists, the above-described latent scratch is present in the vicinity of the pattern on the mask surface. If there is a concave defect due to manifestation or a convex defect due to adhesion of the above foreign matter, the transmitted light of the exposure light undergoes a change in phase angle or a decrease in transmittance due to the concave defect or convex defect. . This change in the phase angle and the decrease in the transmittance cause the positional accuracy and contrast of the transferred pattern to deteriorate. In particular, when short-wavelength light such as ArF excimer laser light (wavelength 193 nm) is used as exposure light, the change in phase angle becomes very sensitive to fine concave defects on the mask surface. The influence becomes large, and changes in phase angle and transmittance due to fine concave defects are important problems that cannot be ignored.

  Even in a binary mask, when light having a short wavelength such as ArF excimer laser light (wavelength: 193 nm) is used as exposure light, even if a minute surface defect is present, the influence on the transmittance becomes large. It becomes a problem. According to the present invention, it is possible to suppress the occurrence of fine surface defects such as concave defects due to the appearance of latent scratches or convex defects due to the adhesion of foreign matter, so that the wavelength required for a fine transfer pattern is 200 nm or less. It is suitable for production of a transfer mask used in an exposure apparatus that uses exposure light having a short wavelength as an exposure light source.

  Multi-tone masks used in the manufacture of FPD (Flat Panel Display) and the like are light-shielding portions that shield exposure light on a glass substrate, semi-transparent portions that transmit exposure light at a predetermined transmittance, and high transmission of exposure light. At least three regions having different transmittances of the translucent part that transmits at a rate are mixed. In recent years, multi-tone masks having two or more types of semi-transparent portions having different transmittances have been used. For this reason, it is very important to control the transmittance of exposure light, and the above-described latent scratches are present on the surface of the glass substrate, resulting in the formation of concave defects and the presence of convex defects due to foreign matter adhesion. That is a problem to avoid. According to the present invention, it is possible to suppress the occurrence of fine surface defects such as concave defects due to the appearance of latent scratches or convex defects due to adhesion of foreign matter, which is suitable for the production of a multi-tone mask. .

For example, it is suitable for the following mask blanks and mask blank substrates used for the production thereof.
(1) A binary mask blank in which the thin film is a light-shielding film made of a material containing a transition metal. The binary mask blank has a light-shielding film on a light-transmitting substrate. , Ruthenium, tungsten, titanium, hafnium, molybdenum, nickel, vanadium, zirconium, niobium, palladium, rhodium, or other transition metal, or a material containing a compound thereof. For example, a light-shielding film composed of chromium or a chromium compound in which one or more elements selected from elements such as oxygen, nitrogen, and carbon are added to chromium. Further, for example, a light shielding film composed of a tantalum compound in which one or more elements selected from elements such as oxygen, nitrogen, and boron are added to tantalum.
Such binary mask blanks include a light shielding film having a two-layer structure of a light shielding layer and a front surface antireflection layer, or a three-layer structure in which a back surface antireflection layer is added between the light shielding layer and the substrate.
Moreover, it is good also as a composition gradient film | membrane from which the composition in the film thickness direction of a light shielding film differs continuously or in steps.

(2) A phase shift mask blank in which the thin film is a light semi-transmissive film made of a material containing a compound of the transition metal and silicon (including transition metal silicide, particularly molybdenum silicide). A halftone phase shift mask having a light semi-transmissive film on a light substrate (glass substrate) and having a shifter portion by patterning the light semi-transmissive film is produced. In such a phase shift mask, in order to prevent a pattern defect of the transferred substrate due to the light semi-transmissive film pattern formed in the transfer region based on the light transmitted through the light semi-transmissive film, the light semi-transmissive is formed on the light-transmissive substrate. The thing which has a form which has a film | membrane and the light shielding film (light shielding zone) on it is mentioned. In addition to halftone phase shift mask blanks, mask blanks for Levenson type phase shift masks and enhancer type phase shift masks, which are substrate digging types in which a translucent substrate is dug by etching or the like to provide a shifter portion. Is mentioned.

  The light-semitransmissive film of the halftone phase shift mask blank transmits light having an intensity that does not substantially contribute to exposure (for example, 1% to 30% with respect to the exposure wavelength). A light semi-transmission part having a phase difference (for example, 180 degrees), and a light semi-transmission part obtained by patterning the light semi-transmission film, and a light transmission that transmits light having an intensity that contributes substantially to exposure without the light semi-transmission film being formed. The light semi-transmission part and the light transmission part by causing the phase of the light to be substantially inverted with respect to the phase of the light transmitted through the light transmission part. The light passing through the vicinity of the boundary and entering the other region by the diffraction phenomenon cancels each other, and the light intensity at the boundary is made almost zero to improve the contrast of the boundary, that is, the resolution.

This light semi-transmissive film is made of a material containing a compound of, for example, a transition metal and silicon (including a transition metal silicide), and includes a material mainly composed of these transition metal and silicon, and oxygen and / or nitrogen. . As the transition metal, molybdenum, tantalum, tungsten, titanium, hafnium, nickel, vanadium, zirconium, niobium, palladium, ruthenium, rhodium, chromium, or the like is applicable.
In the case of having a light-shielding film on the light semi-transmissive film, the material of the light semi-transmissive film contains a transition metal and silicon. It is preferable to have chromium (having etching resistance), particularly chromium, or a chromium compound in which elements such as oxygen, nitrogen, and carbon are added to chromium.

  Since the Levenson type phase shift mask is manufactured from a mask blank having the same configuration as the binary mask blank, the configuration of the pattern forming thin film is the same as that of the light shielding film of the binary mask blank. The light semi-transmissive film of the mask blank for the enhancer-type phase shift mask transmits light having an intensity that does not substantially contribute to exposure (for example, 1% to 30% with respect to the exposure wavelength). This is a film having a small phase difference generated in the exposure light (for example, a phase difference of 30 degrees or less, preferably 0 degrees), and this is different from the light semi-transmissive film of the halftone phase shift mask blank. The material of this light semi-transmissive film includes the same elements as the light semi-transmissive film of the halftone type phase shift mask blank, but the composition ratio and film thickness of each element have a predetermined transmittance and predetermined ratio to the exposure light. The phase difference is adjusted to be small.

(3) Binary mask blank in which the thin film is a light shielding film made of a material containing a compound of transition metal, transition metal and silicon (including transition metal silicide, particularly molybdenum silicide). This light shielding film is a compound of transition metal and silicon And a material mainly composed of these transition metals and silicon and oxygen and / or nitrogen. Examples of the light shielding film include a material mainly composed of a transition metal and oxygen, nitrogen, and / or boron. As the transition metal, molybdenum, tantalum, tungsten, titanium, hafnium, nickel, vanadium, zirconium, niobium, palladium, ruthenium, rhodium, chromium, or the like is applicable.
In particular, when the light shielding film is formed of a molybdenum silicide compound, it has a two-layer structure of a light shielding layer (MoSi, etc.) and a surface antireflection layer (MoSiON, etc.), and the back surface antireflection between the light shielding layer and the substrate. There is a three-layer structure to which layers (MoSiON etc.) are added.
Moreover, it is good also as a composition gradient film | membrane from which the composition in the film thickness direction of a light shielding film differs continuously or in steps.

  In order to form a fine pattern by reducing the thickness of the resist film, an etching mask film may be provided over the light shielding film. This etching mask film has etching selectivity (etching resistance) with respect to etching of the light-shielding film containing transition metal silicide, and in particular, chromium, or a chromium compound in which elements such as oxygen, nitrogen, and carbon are added to chromium. It is preferable to use a material. At this time, by providing the etching mask film with an antireflection function, the transfer mask may be manufactured with the etching mask film remaining on the light shielding film.

(4) A multi-tone mask blank in which the thin film has a laminated structure of one or more semi-transmissive films and a light shielding film.
As for the material of the semi-transmissive film, in addition to the same elements as the light semi-transmissive film of the halftone phase shift mask blank described above, there are also materials containing simple metals such as chromium, tantalum, titanium, aluminum, alloys, or compounds thereof. included. The composition ratio and film thickness of each element are adjusted so as to have a predetermined transmittance with respect to the exposure light. As the light shielding film material, the light shielding film of the binary mask blank can be applied. However, the composition of the light shielding film material and the light shielding film material can have a predetermined light shielding performance (optical density) in a laminated structure with the semi-transmissive film. The film thickness is adjusted.

  Moreover, in said (1)-(4), it has etching tolerance with respect to a light shielding film or a light semi-transmissive film between a translucent board | substrate and a light shielding film, or between a light semi-transmissive film and a light shielding film. An etching stopper film may be provided. The etching stopper film may be a material that can peel off the etching mask film at the same time when the etching stopper film is etched.

The present invention also provides a method for cleaning a transfer mask.
That is, according to the present invention, as in the invention of Configuration 11, the cleaning water to which an ultrasonic wave having a frequency higher than 1.5 MHz is applied is applied to the surface of the transfer mask on which the transfer pattern is formed. Provided is a method for cleaning a transfer mask, characterized by cleaning the surface of the transfer mask.
The transfer mask is produced by patterning the thin film by a photolithography method to form a predetermined transfer pattern using a mask blank in which a transfer pattern forming thin film is formed on the surface of a mask blank substrate. .

  According to the transfer mask cleaning method of the present invention, the frequency is higher than 1.5 MHz even when a cleaning method using cleaning water to which ultrasonic waves are applied is applied in a cleaning process or the like when manufacturing the transfer mask. By washing the surface of the transfer mask with cleaning water to which high ultrasonic waves are applied, it is possible to suppress the occurrence of latent scratches on the translucent part without the transfer pattern and the nearby substrate surface including the transfer pattern. In addition, particles present on the mask surface can be surely eliminated. Therefore, even if periodic cleaning (especially alkali cleaning) for repeated use of the transfer mask is repeated, there is no possibility of forming a concave defect due to latent scratches, and the transfer mask has an abnormal transmittance. And phase abnormalities can be prevented, and film transfer (dropping) of the transfer pattern due to concave defects can be prevented, and the transfer mask can be used safely and continuously. Note that it is preferable to set the frequency of the ultrasonic wave applied to the cleaning water to 2.0 MHz or higher because it is possible to surely suppress the occurrence of latent scratches, and it is optimal to set the frequency of the ultrasonic wave applied to the cleaning water to 2.5 MHz or higher.

  In the transfer mask cleaning method of the present invention, the upper limit of the frequency of the ultrasonic wave applied to the cleaning water is preferably 5.0 MHz or less. If the frequency of the ultrasonic wave applied to the cleaning water is higher than 5.0 MHz, the particle removal rate on the mask surface after cleaning may decrease. Note that it is preferable to set the upper limit of the frequency of the ultrasonic wave applied to the cleaning water to 4.0 MHz or less because the removal rate of relatively large particles can be further improved. The upper limit of the frequency of the ultrasonic wave applied to the cleaning water is preferably 3 It is optimal when the frequency is 5 MHz or less.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples.
(Example 1-1)
The substrate to be used is a synthetic quartz glass substrate (size: 152.4 mm × 152.4 mm, thickness: 6.35 mm). The end surface of this synthetic quartz glass substrate is chamfered and ground, and the glass substrate that has been subjected to rough polishing and precision polishing with a polishing liquid containing cerium oxide abrasive grains is set on a carrier of a double-side polishing apparatus, and the following: Polishing processing (ultra-precision polishing) was performed under the conditions.
Polishing pad: Soft polisher (suede type)
Polishing liquid: colloidal silica abrasive grains (average particle diameter 100 nm) + water Processing pressure: 50 to 100 g / cm ²
Processing time: 60 minutes

  After completion of ultra-precision polishing, cleaning was performed by immersing the glass substrate in hydrofluoric acid to remove the colloidal silica abrasive grains. Next, scrub cleaning, spin cleaning with pure water, and spin drying were performed on the main surface and end surface of the glass substrate. After spin drying, the main surface of the glass substrate is subjected to defect inspection for convex defects and concave defects having a size of 60 nm or more by using a 60 nm sensitivity defect inspection apparatus (M6640 manufactured by Lasertec Corporation) using a laser interference confocal optical system. went. Next, from the glass substrates subjected to the defect inspection, ten sheets having no concave defects detected and the number of detected convex defects equivalent to 60 nm were selected by one digit. Hereinafter, the cleaning ability with respect to the cleaning conditions of each Example was evaluated using the selected glass substrate.

  PSL particles having a particle size of 60 nm were sprinkled as a pseudo foreign material on the main surface of the selected glass substrate. Next, defect inspection was performed on convex defects and concave defects having a size of 60 nm or more with a defect inspection apparatus having a sensitivity of 60 nm (Lasertec M6640). As a result, no concave defects were detected, but 3430 convex defects having a size equivalent to 60 nm or more were detected.

  Subsequently, ultrasonic cleaning was performed using the cleaning apparatus shown in FIG. Pure water was used as the washing water, and an ultrasonic wave having a frequency of 1.6 MHz was applied. In addition, the flow rate of the cleaning water to which ultrasonic waves flowing down from the ultrasonic cleaning nozzle toward the surface (main surface) of the substrate was adjusted to 1.5 liters / minute. The number of substrate rotations during cleaning and the moving speed of the cleaning nozzle were set as appropriate.

The substrate was cleaned for 5 minutes under the above conditions. The main surface of the glass substrate after the cleaning was subjected to defect inspection for convex defects and concave defects having a size of 60 nm or more using the above-described defect inspection apparatus having a sensitivity of 60 nm (M6640 manufactured by Lasertec Corporation). As a result, no concave defects were detected, but 69 convex defects having a size equivalent to 60 nm or more were detected.
Similarly, sprinkling of foreign substances, cleaning, and defect inspection were performed on a total of ten glass substrates.

As a result of calculating the removal rate of particles having a particle size of 60 nm or more on the surface of the substrate after the cleaning on the 10 glass substrates after the above cleaning, the average of 98 glass substrates was 98. It was found that the particle removal rate was as high as 0.0%, and a high cleaning effect was obtained.
Further, after 10 glass substrates having been cleaned as described above were immersed and washed in an alkaline chemical solution for 20 minutes, the main surface of the glass substrate was again used for the defect inspection apparatus having the sensitivity of 60 nm (M6640 manufactured by Lasertec Corporation). As a result of the defect inspection, no concave defect was detected on any of the ten substrates. Therefore, it was confirmed that no latent scratch was generated inside the glass substrate even when the ultrasonic cleaning according to the present invention was performed.

(Examples 1-2 to 1-7, Reference Example 1)
In ultrasonic cleaning, cleaning performance was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 2.0 MHz (Example 1-2).
In ultrasonic cleaning, the cleaning ability was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 2.5 MHz (Example 1-3).
In ultrasonic cleaning, the cleaning ability was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 3.0 MHz (Example 1-4).
In ultrasonic cleaning, the cleaning ability was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 3.5 MHz (Example 1-5).

In ultrasonic cleaning, the cleaning ability was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 4.0 MHz (Example 1-6).
In ultrasonic cleaning, the cleaning ability was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 5.0 MHz (Example 1-7).
In the ultrasonic cleaning, the cleaning ability was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 6.0 MHz (Reference Example 1).

  Similarly to Example 1-1, defect inspection was performed on the main surface of the substrate before and after cleaning, and the removal rate of particles having a particle size of 60 nm or more on the substrate surface after cleaning was calculated. As a result, in the case of Example 1-2, in the defect inspection on the main surface of the substrate before cleaning, concave defects were not detected, and 4080 convex defects having a size equivalent to 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defects were detected, and 90 convex defects having a size equivalent to 60 nm or more were detected. Further, when the removal rate of particles having a particle size of 60 nm or more on the substrate surface after cleaning was calculated, the average particle size of 10 glass substrates was 97.8%, which is a high particle removal rate. However, it was found that a high cleaning effect can be obtained.

  In the case of Example 1-3, in the defect inspection of the main surface of the substrate before cleaning, no concave defect was detected, and 2840 convex defects having a size of 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defect was detected, and 71 convex defects having a size equivalent to 60 nm or more were detected. Further, when the removal rate of particles having a particle size equivalent to 60 nm or more on the substrate surface after cleaning was calculated, the average particle removal rate of 10 glass substrates was 97.5%, which is the case of Example 1-3. However, it was found that a high cleaning effect can be obtained.

  In the case of Example 1-4, in the defect inspection of the main surface of the substrate before cleaning, no concave defect was detected, and 2545 convex defects having a size of 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defect was detected, and 76 convex defects having a size of 60 nm or more were detected. Furthermore, when the removal rate of particles having a particle size of 60 nm or more on the substrate surface after cleaning was calculated, the average particle size of 10 glass substrates was 97.0%, which is a high particle removal rate. In the case of Example 1-4 However, it was found that a high cleaning effect can be obtained.

  In the case of Example 1-5, in the defect inspection on the main surface of the substrate before cleaning, no concave defect was detected, and 2911 convex defects having a size equivalent to 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defect was detected, and 99 convex defects having a size equivalent to 60 nm or more were detected. Furthermore, when the removal rate of particles having a particle size equivalent to 60 nm or more on the substrate surface after cleaning was calculated, the average particle removal rate of 10 glass substrates was 96.6%, which is the case of Example 1-5. However, it was found that a high cleaning effect can be obtained.

In the case of Example 1-6, in the defect inspection of the main surface of the substrate before cleaning, no concave defect was detected, and 5133 convex defects having a size equivalent to 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defects were detected, and 185 convex defects having a size of 60 nm or more were detected. Furthermore, when the removal rate of particles having a particle size equivalent to 60 nm or more on the substrate surface after cleaning was calculated, the average particle size of 10 glass substrates was 96.4%, which is a high particle removal rate. In the case of Example 1-6 However, it was found that a high cleaning effect can be obtained.
In the case of Example 1-7, in the defect inspection of the main surface of the substrate before cleaning, no concave defect was detected, and 3256 convex defects having a size of 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defects were detected, and 163 convex defects having a size equivalent to 60 nm or more were detected. Furthermore, when the removal rate of particles having a particle size of 60 nm or more on the substrate surface after cleaning was calculated, the average particle removal rate of 10 glass substrates was as high as 95.0%. In the case of Example 1-7 However, it was found that a high cleaning effect can be obtained.

  On the other hand, in the case of Reference Example 1, in the defect inspection of the main surface of the substrate before cleaning, no concave defect was detected, and 4874 convex defects having a size of 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defects were detected, and 370 convex defects having a size of 60 nm or more were detected. Further, when the removal rate of particles having a particle size equivalent to 60 nm or more on the substrate surface after cleaning was calculated, the average of the 10 glass substrates was 92.4%, which was slightly lower than the other examples. I understood that. In Reference Example 1, cleaning performance evaluation using PSL particles having a particle size of 200 nm was also performed under cleaning conditions. However, the defect detection rate was clearer than cleaning performance evaluation performed using PSL particles having a particle size of 60 nm. The result of rising was obtained.

  Further, as in Example 1-1, after the cleaned glass substrate was immersed and washed in an alkaline chemical for 20 minutes, the defect inspection of the main surface of the glass substrate was performed again. No concave defects were detected on any of the substrates of ˜1-7 and Reference Example 1. Therefore, it was confirmed that no latent scratch was generated inside the glass substrate when the ultrasonic cleaning according to the present invention was performed.

(Example 2)
As in Example 1-1, the main surface of the glass substrate after spin drying was inspected using a defect inspection apparatus with a sensitivity of 60 nm (M6640 manufactured by Lasertec Corporation), a concave defect was not detected, and a convex shape equivalent to 60 nm. The number of defects detected was selected by one digit. Using the selected glass substrate, a phase shift mask blank was produced as follows.
First, a light semi-transmissive film made of nitrided molybdenum and silicon was formed on the glass substrate.
Specifically, using a mixed target of molybdenum (Mo) and silicon (Si) (Mo: Si = 10 mol%: 90 mol%), mixing argon (Ar), nitrogen (N ₂ ), and helium (He). In a gas atmosphere (gas flow ratio Ar: N ₂ : He = 5: 49: 46), a gas pressure of 0.3 Pa, a DC power source power of 3.0 kW, and reactive sputtering (DC sputtering), molybdenum, silicon, and A MoSiN film made of nitrogen was formed to a thickness of 69 nm. Next, the substrate on which the MoSiN film was formed was subjected to heat treatment using a heating furnace in the atmosphere at a heating temperature of 450 ° C. and a heating time of 1 hour. This MoSiN film had an transmittance of 6.16% and a phase difference of 184.4 degrees in an ArF excimer laser.

Next, the following light shielding film was formed on the light semi-transmissive film.
Specifically, a chromium (Cr) target is used as a sputtering target, and a mixed gas atmosphere of argon (Ar), carbon dioxide (CO ₂ ), nitrogen (N ₂ ), and helium (He) (gas pressure 0.2 Pa, Gas flow ratio Ar: CO ₂ : N ₂ : He = 20: 35: 10: 30), the power of the DC power source is 1.7 kW, and a 30 nm thick CrOCN layer is formed by reactive sputtering (DC sputtering). Filmed. Subsequently, a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) (gas pressure 0.1 Pa, gas flow ratio Ar: N ₂ = 25: 5) was set, and the power of the DC power source was set to 1.7 kW. A 4 nm thick CrN layer was formed by reactive sputtering (DC sputtering). Finally, a mixed gas atmosphere of argon (Ar), carbon dioxide (CO ₂ ), nitrogen (N ₂ ), and helium (He) (gas pressure 0.2 Pa, gas flow ratio Ar: CO ₂ : N ₂ : He = 20: 35: 5: 30), the power of the DC power source is 1.7 kW, and a CrOCN layer having a film thickness of 14 nm is formed by reactive sputtering (DC sputtering). A chromium-based light shielding film was formed.

  This light-shielding film has a laminated structure with the light semi-transmissive film and is adjusted so that the optical density (OD) is 3.0 at a wavelength of 193 nm of ArF excimer laser exposure light. The surface reflectance of the light shielding film with respect to the wavelength of the exposure light was 20%.

  As described above, with respect to the mask blank in which the light semi-transmissive film and the light-shielding film are laminated on the glass substrate, the main surface of the mask blank is equivalent to 60 nm or more by using a 60 nm sensitivity defect inspection apparatus (M6640 manufactured by Lasertec Corporation). Defect inspection was conducted for convex defects and concave defects of a size of. Next, from the glass substrates subjected to the defect inspection, ten sheets having no concave defects detected and the number of detected convex defects equivalent to 60 nm were selected by one digit. PSL particles having a particle size of 60 nm were dispersed as pseudo foreign matters on the main surface of the selected mask blank. Next, defect inspection was performed on convex defects and concave defects having a size of 60 nm or more with a defect inspection apparatus having a sensitivity of 60 nm (Lasertec M6640). As a result, no concave defects were detected, but 3377 convex defects having a size equivalent to 60 nm or more were detected.

  Subsequently, ultrasonic cleaning was performed using the cleaning apparatus shown in FIG. Pure water was used as the washing water, and an ultrasonic wave having a frequency of 1.6 MHz was applied. Further, the flow rate of the cleaning water to which the ultrasonic wave flowing down from the ultrasonic cleaning nozzle toward the thin film surface of the mask blank was applied was adjusted to 1.5 liters / minute. The mask blank rotation speed during cleaning and the moving speed of the cleaning nozzle were set as appropriate.

The ultrasonic cleaning for 5 minutes was performed on the above conditions. The main surface of the mask blank after cleaning was subjected to defect inspection for convex defects and concave defects having a size of 60 nm or more using the above-described 60 nm sensitivity defect inspection apparatus (M6640 manufactured by Lasertec Corporation). As a result, no concave defects were detected, but 74 convex defects having a size equivalent to 60 nm or more were detected.
Similarly, sprinkling of foreign substances, cleaning, and defect inspection were performed on a total of 10 mask blanks.

As in Example 1-1, for the 10 mask blanks that have been cleaned, the removal rate of particles having a particle size equivalent to 60 nm or more on the main surface of the mask blank after cleaning was calculated based on the relational expression described above. It was found that a high particle removal rate of 97.8% was obtained and a high cleaning effect was obtained.
As described above, a phase shift mask blank having a thin film for pattern formation having a laminated structure of a light semitransmissive film and a light shielding film on a glass substrate was produced.

Next, a halftone phase shift mask was produced using the above phase shift mask blank.
First, a chemically amplified positive resist film for electron beam drawing (PRL009 manufactured by Fuji Film Electronics Materials) was formed as a resist film on the mask blank. The resist film was formed by spin coating using a spinner (rotary coating apparatus). After applying the resist film, a predetermined heat drying treatment was performed. The film thickness of the resist film was 150 nm.

Next, a desired pattern was drawn on the resist film formed on the mask blank using an electron beam drawing apparatus, and then developed with a predetermined developer to form a resist pattern.
Next, the light shielding film was etched using the resist pattern as a mask. A mixed gas of Cl ₂ and O ₂ was used as a dry etching gas. Subsequently, the light semi-transmissive film (MoSiN film) was etched to form a light semi-transmissive film pattern. A mixed gas of SF ₆ and He was used as the dry etching gas.

Next, the remaining resist pattern is peeled off, the same resist film as above is formed again on the entire surface, and drawing is performed to form a light-shielding band on the outer periphery of the mask. A pattern was formed. Using this resist pattern as a mask, the light shielding film other than the light shielding zone region was removed by etching.
The remaining resist pattern was peeled off to obtain a phase shift mask.
In the phase shift mask thus obtained, a 45 nm half pitch fine pattern was formed with good pattern accuracy.

  In addition, after the obtained phase shift mask was immersed and washed in an alkaline chemical for 20 minutes, the phase shift mask was inspected again using a mask defect inspection apparatus, and as a result, a transparent portion without a mask pattern was obtained. No concave defect was detected. Also, no pattern omission was detected. Therefore, it was confirmed that even if the ultrasonic cleaning according to the present invention was performed on the mask blank in which the light semi-transmissive film and the light shielding film were laminated on the glass substrate, no latent scratch was generated inside the glass substrate. .

(Example 3)
As in Example 1-1, the main surface of the glass substrate after spin drying was inspected using a defect inspection apparatus with a sensitivity of 60 nm (M6640 manufactured by Lasertec Corporation), a concave defect was not detected, and a convex shape equivalent to 60 nm. The number of defects detected was selected by one digit. Using the selected glass substrate, a binary mask blank was produced as follows.
On the glass substrate, a MoSiN film (light-shielding layer) and a MoSiN film (surface antireflection layer) were formed as light-shielding films, respectively.
Specifically, using a mixed target of Mo and Si (Mo: Si = 13 at%: 87 at%), in a mixed gas atmosphere of Ar and N ₂ , a MoSiN film (film composition ratio) made of molybdenum, silicon, and nitrogen Mo: 9.9 at%, Si: 66.1 at%, N: 24.0 at%) were formed with a film thickness of 47 nm.

Next, using a target of Mo: Si = 13 at%: 87 at%, a MoSiN film made of molybdenum, silicon, and nitrogen was formed to a thickness of 13 nm in a mixed gas atmosphere of Ar and N ₂ . The total thickness of the light shielding film was 60 nm.
The optical density (OD) of the light-shielding film was 3.0 at a wavelength of 193 nm of ArF excimer laser exposure light.

Next, the following Cr etching mask film was formed on the MoSi light shielding film.
Specifically, a chromium (Cr) target is used as a sputtering target, and a 5 nm thick CrN film (film) is formed by reactive sputtering (DC sputtering) in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ). Composition ratio Cr: 75.3 at%, N: 24.7 at%) was formed. Note that Rutherford backscattering analysis was used for elemental analysis of each layer of the light shielding film and the Cr-based etching mask film.

  As described above, with respect to the mask blank in which the MoSi-based light-shielding film and the Cr-based etching mask film are laminated on the glass substrate, the main surface of the mask blank is used with a defect inspection apparatus having a sensitivity of 60 nm (M6640 manufactured by Lasertec Corporation). Defect inspection was performed for convex defects and concave defects having a size of 60 nm or more. Next, from the glass substrates subjected to the defect inspection, ten sheets having no concave defects detected and the number of detected convex defects equivalent to 60 nm were selected by one digit. PSL particles having a particle size of 60 nm were dispersed as pseudo foreign matters on the main surface of the selected mask blank. Next, defect inspection was performed on convex defects and concave defects having a size of 60 nm or more with a defect inspection apparatus having a sensitivity of 60 nm (Lasertec M6640). As a result, no concave defect was detected, but 3892 convex defects having a size of 60 nm or more were detected.

  Subsequently, ultrasonic cleaning was performed using the cleaning apparatus shown in FIG. Pure water was used as the washing water, and an ultrasonic wave having a frequency of 1.6 MHz was applied. Further, the flow rate of the cleaning water to which the ultrasonic wave flowing down from the ultrasonic cleaning nozzle toward the thin film surface of the mask blank was applied was adjusted to 1.5 liters / minute. The mask blank rotation speed during cleaning and the moving speed of the cleaning nozzle were set as appropriate.

The ultrasonic cleaning for 5 minutes was performed on the above conditions. The main surface of the mask blank after cleaning was subjected to defect inspection for convex defects and concave defects having a size of 60 nm or more using the above-described 60 nm sensitivity defect inspection apparatus (M6640 manufactured by Lasertec Corporation). As a result, no concave defect was detected, but 70 convex defects having a size of 60 nm or more were detected.
Similarly, sprinkling of foreign substances, cleaning, and defect inspection were performed on a total of 10 mask blanks.

As in Example 1-1, for the 10 mask blanks that have been cleaned, the removal rate of particles having a particle size equivalent to 60 nm or more on the main surface of the mask blank after cleaning was calculated based on the relational expression described above. It was found that a high particle removal rate of 98.2% was obtained and a high cleaning effect was obtained.
As described above, a binary mask blank having a MoSi light shielding film and a Cr etching mask film on a glass substrate was produced.

Next, a binary mask was produced using the above binary mask blank.
First, a chemically amplified positive resist film for electron beam drawing (PRL009 manufactured by Fuji Film Electronics Materials) was formed as a resist film on the mask blank. The resist film was formed by spin coating using a spinner (rotary coating apparatus). After applying the resist film, a predetermined heat drying treatment was performed. The film thickness of the resist film was 100 nm.

Next, a desired pattern was drawn on the resist film formed on the mask blank using an electron beam drawing apparatus, and then developed with a predetermined developer to form a resist pattern.
Next, the etching mask film was etched using the resist pattern as a mask. A mixed gas of Cl ₂ and O ₂ was used as a dry etching gas. Subsequently, the MoSi-based light-shielding film (MoSiN / MoSiN) was etched using the pattern formed on the etching mask film as a mask to form a light-shielding film pattern. A mixed gas of SF ₆ and He was used as the dry etching gas.

Next, the remaining resist pattern was peeled off, and the etching mask film pattern was removed by etching.
In the MoSi binary mask thus obtained, a fine pattern of 32 nm half pitch was formed with good pattern accuracy.
Moreover, after immersing and cleaning the obtained binary mask in an alkaline chemical for 20 minutes, the defect inspection of the binary mask was performed again using a mask defect inspection apparatus, and as a result, a concave defect was found in the translucent part having no mask pattern. Was not detected. Also, no pattern omission was detected. Therefore, even if ultrasonic cleaning according to the present invention is performed on the mask blank obtained by laminating the MoSi-based light-shielding film and the Cr-based etching mask film on the glass substrate, there is no occurrence of latent scratches inside the glass substrate. It could be confirmed.

(Comparative Example 1)
In the ultrasonic cleaning, the cleaning ability was evaluated in the same manner as in Example 1-1 except that the frequency of the ultrasonic wave applied to the cleaning water was changed to 1.5 MHz.
Similarly to Example 1-1, defect inspection was performed on the main surface of the substrate before and after cleaning, and the removal rate of particles having a particle size of 60 nm or more on the substrate surface after cleaning was calculated. As a result, in the defect inspection of the main surface of the substrate before cleaning, concave defects were not detected, and 3119 convex defects having a size equivalent to 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defects were detected, and 37 convex defects having a size of 60 nm or more were detected. Furthermore, when the removal rate of particles having a particle size equivalent to 60 nm or more on the substrate surface after cleaning was calculated, the average particle size of 10 glass substrates was 98.8%, and a high cleaning effect was obtained. I understood.

  However, as in Example 1-1, after the glass substrate that had been cleaned was immersed and washed in an alkaline chemical for 20 minutes, the defect inspection of the main surface of the glass substrate was performed again. A concave defect was detected on the substrate. In other words, since no concave defects were detected on the substrate surface before cleaning, when ultrasonic cleaning according to the above comparative example was performed, latent scratches occurred inside the glass substrate, and this was caused by the action of alkaline chemicals. As a result, it was confirmed that

(Comparative Example 2)
A mask blank similar to Example 2 except that the frequency of the ultrasonic wave applied to the cleaning water is changed to 1.5 MHz for the mask blank in which the light semi-transmissive film and the light shielding film are laminated. A blank was ultrasonically cleaned.
Similarly to Example 2, the defect inspection of the mask blank main surface before and after cleaning was performed, and the removal rate of particles having a particle size of 60 nm or more on the mask blank main surface after cleaning was calculated. As a result, in the defect inspection of the main surface of the substrate before cleaning, concave defects were not detected, and 2774 convex defects having a size of 60 nm or more were detected. On the other hand, in the defect inspection of the main surface of the substrate after cleaning, no concave defects were detected, and 22 convex defects having a size of 60 nm or more were detected. Furthermore, when the removal rate of particles having a particle size of 60 nm or more on the substrate surface after cleaning was calculated, the average particle size of 10 glass substrates was 99.2%, and a high cleaning effect was obtained. I understood.
As described above, a phase shift mask blank having a thin film for pattern formation having a laminated structure of a light semitransmissive film and a light shielding film on a glass substrate was produced.

Next, in the same manner as in Example 2, a halftone phase shift mask was produced using the above phase shift mask blank.
After the obtained phase shift mask was immersed and washed in an alkaline chemical for 20 minutes, the surface of the phase shift mask was inspected again. As a result, a concave defect was detected in the translucent part having no mask pattern. That is, since no concave defect was originally detected on the used glass substrate surface, the ultrasonic cleaning according to the comparative example 2 was performed on the mask blank in which the light semi-transmissive film and the light shielding film were laminated on the glass substrate. When this was done, it was confirmed that a latent flaw occurred inside the glass substrate, and this latent flaw became apparent as a concave defect due to the action of the alkaline chemical solution in the translucent part.

  Therefore, in Comparative Example 2, the occurrence of latent scratches that cannot be confirmed during the manufacture of the mask blank is detected for the first time when the transfer mask is produced using this mask blank and becomes manifest as a concave defect. Since a problem occurs, in the case of cleaning a mask blank, it is very important not to cause latent scratches inside the glass substrate. On the other hand, according to the present invention, as described above, since it is possible to suppress the occurrence of latent scratches inside the glass substrate during cleaning of the mask blank, after the transfer mask is manufactured using this mask blank, The problem that the flaw is not found until the scratch becomes obvious as a concave defect does not occur, and the effect of the present invention is very large.

1 Substrate 10 Cleaning Device 11 Spin Chuck 12 Electric Motor 13 Cleaning Cup 14 Ultrasonic Cleaning Nozzle 15 Arm 16 Cleaning Liquid Supply Device

Claims (12)

While rotating the substrate made of a glass material, it has a cleaning process in which cleaning water to which ultrasonic waves having a frequency of 2.0 MHz or more and 5.0 MHz or less are applied from the cleaning nozzle is supplied so as to hit the main surface of the substrate. A method for manufacturing a mask blank substrate. The method for manufacturing a mask blank substrate according to claim 1, wherein the cleaning step discharges cleaning water while moving the cleaning nozzle from the center to the end surface of the main surface of the substrate. 3. The method for manufacturing a mask blank substrate according to claim 1, wherein the flow rate of the cleaning water is 1.0 liter / minute or more and 5.0 liter / minute or less. The surface of the substrate after cleaning, removal rate for pre-cleaning particle size 60nm equivalent or more particles, the mask blank according to any one of claims 1 to 3, wherein 95% or more A method for manufacturing a substrate. The substrate is a substrate for a binary mask blank substrate for phase shift mask blank or substrate for mask blank according to any one of claims 1 to 4, characterized in that a substrate for a multi-tone mask blank, Production method. A thin film for forming a transfer pattern is formed on the surface of the mask blank substrate obtained by the method for manufacturing a mask blank substrate according to any one of claims 1 to 5. Manufacturing method. A film forming process for forming a thin film for forming a transfer pattern on the surface of a substrate made of a glass material, and a frequency of 2.0 MHz to 5.0 MHz from a cleaning nozzle while rotating the substrate on which the thin film is formed. And a cleaning step of supplying and cleaning the cleaning water to which the ultrasonic wave is applied so as to hit the surface of the thin film. 8. The method of manufacturing a mask blank according to claim 7, wherein in the cleaning step, cleaning water is discharged while moving the cleaning nozzle from the center to the end surface of the surface of the thin film. The method of manufacturing a mask blank according to claim 7 or 8, wherein the flow rate of the cleaning water is 1.0 liter / minute or more and 5.0 liter / minute or less. 10. The mask blank according to claim 7 , wherein a removal rate of particles having a particle size of 60 nm or more before cleaning on the surface of the thin film after cleaning is 95% or more. Production method. The method of manufacturing a mask blank according to any one of claims 7 to 10 , wherein the mask blank is a binary mask blank, a phase shift mask blank, or a multi-tone mask blank. A method for manufacturing a transfer mask, comprising patterning the thin film of a mask blank obtained by the method for manufacturing a mask blank according to any one of claims 6 to 11 to form a transfer pattern.

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